Synfacts 2005(2): 0207-0207  
DOI: 10.1055/s-2005-916059
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart · New York

Green Chemistry: Synthesis of Quinolines

Contributor(s): Victor Snieckus, Till Vogel
K. Taguchi, S. Sakaguchi, Y. Ishii*
Kansai University, Osaka, Japan
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Publikationsverlauf

Publikationsdatum:
25. Oktober 2005 (online)

Significance

A modification of the Friedländer reaction (2-aminobenzaldehydes with aliphatic ketones and aldehydes), one of the most widely used methods for the preparation of quinolines, is reported. The iridium-catalyzed modified Friedländer protocol is environmentally advantageous in that it proceeds under solvent-free conditions in the presence of solid KOH to give quinolines in good yields (63-91%). The addition of 4 mol% of Ph3P slightly increases the yields. The reaction is likely to proceed via ketimine formation followed by an oxidative step and an intramolecular aldol-type condensation. A further feature is the excellent regioselectivity (exception: R2 = n-pentyl). An extension to the synthesis of pyrroles is also described.